With the advent of compact digital technology it becomes increasingly possible to introduce and implement various digital signal-processing methods in a range of products enhancing significantly their performance. Digital video and still cameras are good candidates for such integration. Modern cameras employ sensors, such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), which are sampled to produce a digital signal, which is further processed by a special purpose DSP (Digital Signal Processing) device.
First approaches to temporal noise reduction appeared in literature in the early eighties (see for example, U.S. Pat. No. 4,296,436 (Achiha), and E. Dubois, “Noise Reduction in Image Using Motion-Compensated Temporal Filtering”, IEEE Transactions on Communications, vol. COM-32, No. 7, pp. 826-831 (July 1984)). In these works simple adaptation of filter coefficients based on the difference between the incoming frame and the frame previously stored in the memory was used to adaptively smooth camera noise. In cases where motion is substantial, filter coefficients were chosen such that mostly the current frame reflecting the moving object was presented in the final image, whereas in areas with low-motion the temporal filtering have been strong leading to the significant noise suppression. Various modifications of the basic scheme have been introduced during the following years (see U.S. Pat. No. 5,600,731 (Sezan et al.), and U.S. Pat. No. 5,442,407 (Iu)). Later on, the methods for adaptive temporal filtering have been adopted for various applications, such as adaptive cleaning of the MPEG movies (U.S. Pat. No. 6,281,942 (Wang)) and using the local vs. global motion estimation considerations (U.S. Pat. No. 6,115,502, (De Haan et al.)).